The Cardiology Advisory panel of the NHLBI has concluded that electrically powered artificial hearts provide the best hope for acceptable patient life style, particularly with regard to portability and tether-free operation. We concur and hypothesize that "permanent circulatory support is feasible with electrically powered total artificial hearts which successfully meet all physiological, anatomic, psychological, economic and other criteria for human use." We propose to identify and quantitate physiologic and engineering requirements specifically relevant to total hearts as opposed to LVAD's. We will initially conduct mock circulation studies followed by in vivo work using the reversing electrohydraulic energy converter developed under NHLBI contract for LVAD's and adapted to total heart use. Seven hypotheses are to be tested which address questions of alternate pumping, physiologic control and long-term in vivo function, surgical implantation of one-piece devices, infection and septic thromboembolism, durability and adequacy of function to permit moderate exercise. The data from electrically powered total hearts will be compared to controls implanted with pneumatic hearts (funded independently of this proposal). We do not intend to develop a total heart acceptable for human use under this grant, but rather to provide basic data necessary for its eventual success.